delaunayfast exception

Hi!

I'd like to report an exception:
Exception occurred during event dispatching:
visad.SetException: Delaunay.finish_triang: error in triangulation!
        at visad.Delaunay.finish_triang(Compiled Code)
        at visad.DelaunayFast.<init>(Compiled Code)

With the same data, I have no troubles to run DelaunayWatson but
DelaunayFast throws the exception above. What am I doing wrong?

regards,

Jure